Method of Manufacturing a Semiconductor Device and a Semiconductor Workpiece

ABSTRACT

A semiconductor device is manufactured in a semiconductor substrate comprising a first main surface, the semiconductor substrate including chip areas. The method of manufacturing the semiconductor substrate comprises forming components of the semiconductor device in the first main surface in the chip areas, removing substrate material from a second main surface of the semiconductor substrate, the second main surface being opposite to the first main surface, forming a separation trench into a first main surface of the semiconductor substrate, the separation trench being disposed between adjacent chip areas. The method further comprises forming at least one sacrificial material in the separation trench, and removing the at least one sacrificial material from the trench.

TECHNICAL FIELD

The present disclosure relates to a method of manufacturing asemiconductor device and to a semiconductor workpiece.

RELATED BACKGROUND

Power devices, for example, MOS power transistors attempt to achieve asmall on-resistance which is defined by R_(on)·area, while at the sametime achieving a high breakdown voltage Vds when being in an off state.Approaches have been made to manufacture these power transistors on thinto ultra-thin substrates having a thickness of less than 100 μm, forexample 70 μm or less and having even a thickness of 10 to 20 μm,depending on the voltage class in which the device is being employed.

According to generally employed semiconductor manufacturing processes,components of semiconductor devices are processed by processingsemiconductor wafers. After manufacturing the single devices, the waferis isolated into single chips. When semiconductor devices aremanufactured on thin substrates, problems may arise when isolating thesingle chips by conventional isolation or dicing processes.

SUMMARY

According to an embodiment, a method of manufacturing a semiconductordevice comprises forming a separation trench into a first main surfaceof a semiconductor substrate, forming at least one sacrificial materialin the separation trench. The method further includes removing substratematerial from a second main surface of the semiconductor substrate, thesecond main surface being opposite to the first main surface, so as touncover a bottom side of the trench. The method further includesremoving the at least one sacrificial material from the bottom side ofthe trench, after the substrate material has been removed from thesecond main surface.

According to an embodiment, a semiconductor workpiece comprises asemiconductor substrate, at least two chip areas, components ofsemiconductor devices being formed in the semiconductor substrate in thechip areas, and a separation trench being disposed between adjacent chipareas. The separation trench is formed in a first main surface of thesemiconductor substrate and extends from the first main surface to asecond main surface of the semiconductor substrate, the second mainsurface being disposed opposite to the first main surface. Theseparation trench is filled with at least one sacrificial material.

According to an embodiment, a method of manufacturing a semiconductordevice in a semiconductor substrate comprising a first main surface, thesemiconductor substrate including chip areas, includes formingcomponents of the semiconductor device in the first main surface in thechip areas, removing substrate material from a second main surface ofthe semiconductor substrate, the second main surface being opposite tothe first main surface, forming a separation trench into a first mainsurface of a semiconductor substrate, the separation trench beingdisposed between adjacent chip areas, forming at least one sacrificialmaterial in the separation trench, and removing the at least onesacrificial material from the trench.

Those skilled in the art will recognize additional features andadvantages upon reading the following detailed description and onviewing the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification. The drawings illustrate the embodiments ofthe present invention and together with the description serve to explainprinciples of the invention. Other embodiments of the invention andintended advantages will be readily appreciated as they become betterunderstood by reference to the following detailed description.

FIGS. 1A to 1J illustrate a method of manufacturing a semiconductordevice according to an embodiment;

FIGS. 2A to 2H illustrate a method of manufacturing a semiconductordevice according to a further embodiment;

FIGS. 3A to 3E illustrate a method of manufacturing a semiconductordevice according to an embodiment;

FIGS. 4A to 4F illustrate a method of manufacturing a semiconductordevice according to a further embodiment;

FIG. 5 schematically illustrates a method of manufacturing asemiconductor device according to an embodiment; and

FIGS. 6A and 6B schematically illustrate a method of manufacturing asemiconductor device according to further embodiments.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings, which form a part hereof, and in which are shownby way of illustrations specific embodiments in which the invention maybe practiced. It is to be understood that other embodiments may beutilized and structural or logical changes may be made without departingfrom the scope of the present invention. For example, featuresillustrated or described for one embodiment can be used on or inconjunction with other embodiments to yield yet a further embodiment. Itis intended that the present invention includes such modifications andvariations. The examples are described using specific language whichshould not be construed as limiting the scope of the appending claims.The drawings are not scaled and are for illustrative purposes only. Forclarity, the same elements have been designated by correspondingreferences in the different drawings if not stated otherwise.

The terms “having”, “containing”, “including”, “comprising” and the likeare open and the terms indicate the presence of stated structures,elements or features but not preclude additional elements or features.The articles “a”, “an” and “the” are intended to include the plural aswell as the singular, unless the context clearly indicates otherwise.

The term “electrically connected” describes a permanent low-ohmicconnection between electrically connected elements, for example a directcontact between the concerned elements or a low-ohmic connection via ametal and/or highly doped semiconductor.

The terms “wafer”, “substrate” or “semiconductor substrate” used in thefollowing description may include any semiconductor-based structure thathas a semiconductor surface. Wafer and structure are to be understood toinclude silicon, silicon-on-insulator (SOI), silicon-on sapphire (SOS),doped and undoped semiconductors, epitaxial layers of silicon supportedby a base semiconductor foundation, and other semiconductor structures.The semiconductor need not be silicon-based. The semiconductor could aswell be silicon-germanium, germanium, or gallium arsenide. According toembodiments of the present application, generally, silicon carbide (SiC)or gallium nitride (GaN) is a further example of the semiconductorsubstrate material.

The term “vertical” as used in this specification intends to describe anorientation which is arranged perpendicular to the first surface of thesemiconductor substrate or semiconductor body.

The terms “lateral” and “horizontal” as used in this specificationintends to describe an orientation parallel to a first surface of asemiconductor substrate or semiconductor body. This can be for instancethe surface of a wafer or a die.

Generally, for patterning material layers, a photolithographic methodmay be used in which a suitable photoresist material is provided. Thephotoresist material is photolithographically patterned using a suitablephotomask. The patterned photoresist layer can be used as a mask duringsubsequent processing steps. For example, as is common, a hardmask layeror a layer made of a suitable material such as silicon nitride,polysilicon or carbon may be provided over the material layer to bepatterned. The hardmask layer is photolithographically patterned usingan etching process, for example. Taking the patterned hardmask layer asan etching mask, the material layer is patterned.

FIG. 1A shows a cross-sectional view of a semiconductor workpieceaccording to an embodiment, which may form a starting point forimplementing a method according to an embodiment. Alternatively, theworkpiece may be obtained when performing the method according to anembodiment.

The workpiece may comprise a semiconductor substrate 100 having a firstmain surface 110 and a second main surface 120. The workpiece comprisesa chip area 150 and a kerf area 155. Generally, in a semiconductorsubstrate such as a semiconductor wafer, a plurality of chip areas 150are defined, adjacent chip areas 150 being separated from each other bya kerf area 155. Components of semiconductor devices are formed in eachof the chip areas 150. For example, transistors 160 and othersemiconductor devices may be formed in each of the chip areas 150. Thesemiconductor devices may comprise doped regions 161, conductive lines221 or pads, and insulating material. For example, components of thesemiconductor devices may be formed in the semiconductor substrate 100or in a region adjacent to a first main surface 110 of the semiconductorsubstrate 100. Further components of the semiconductor devices may bedisposed outside the semiconductor substrate 100. For example,conductive lines 221, contact pads and other components may be formedover the semiconductor substrate 100 and may, for example, be disposedwithin an insulating layer 225. The chip area 150 may further compriseisolation trenches 130 being filled with at least one insulatingmaterial 131 such as silicon oxide. A further insulating or conductivematerial 132 may be disposed in the isolation trenches 130, the furtherinsulating or conductive material 132 being insulated from the substratematerial 100 by the insulating layer 131. For example, these isolationtrenches 130 may insulate adjacent portions of the chip area 150.

According to further embodiments, contact trenches having a similarconstruction as the isolation trenches 130 may be disposed within thesemiconductor substrate 100. For example, the further insulating orconductive material 132 may be conductive, so that an electrical contactfrom the first main surface 110 to the second main surface 120 may beaccomplished by the further insulating or conductive material 132. Forexample, a distance between the first main surface 110 and the secondmain surface 120 may be less than 100 μm, for example, less than 60 μm,for example 40 μm.

In the embodiment shown in FIG. 1A, an insulating layer 225 is disposedover the first main surface 110 of the semiconductor substrate 100. Asurface of the insulating layer 225 defines a surface 210 of theworkpiece 200.

Further, on a back side of the semiconductor substrate 100, a furtherinsulating layer 235 may be disposed so as to define a workpiece backside 220. Within the kerf area 155, for example, test structures, pads,contact pads 230 may be disposed so as to fulfil several functionsaccording to specific needs. For example, test structures or patternsfor monitoring a wafer processing method may be arranged in the kerfarea 155.

In the embodiment illustrated in FIG. 1A, a separation trench 140 isdisposed between the kerf area 155 and an adjacent chip area 150. Theseparation trench 140 is formed in the first main surface 110 of thesemiconductor substrate 100. The separation trench 140 extends in adirection intersecting the illustrated plane of the drawing. Forexample, the separation trench 140 may extend perpendicularly withrespect to the plane of the drawing. According to a further embodiment,depending on the desired shape of the resulting chips, the separationtrench 140 may extend in an arbitrary direction intersecting the planeof the drawing. The separation trench 140 is filled with at least onesacrificial material. For example, the sacrificial material may comprisea first sacrificial layer 141 which may be insulating. The firstsacrificial layer 141 is disposed adjacent to a sidewall of theseparation trench 140. The first sacrificial layer 141 extends along thesidewall of the separation trench 140 to a bottom side 144 thereof.Moreover, the interior of the separation trench 140 may be filled with asecond sacrificial layer 142 which is different from the first material.For example, the first layer 141 may be insulating and the secondsacrificial layer 142 may be conductive. In the embodiment illustratedin FIG. 1A, the separation trench 140 extends from the first mainsurface 110 of the semiconductor substrate 100 to the second mainsurface 120 of the semiconductor substrate 100. The separation trench140 may be completely filled with the sacrificial material so that thesacrificial filling is flush with the first main surface 110. Thesacrificial material may comprise silicon oxide, for example, thermallygrown silicon oxide, silicon nitride or polysilicon and any combinationof these materials. According to the embodiment illustrated in FIG. 1A,the workpiece surface 210 may be a planar surface. Further, thesemiconductor substrate 100 may be attached to a front side carrier 300such as a glass carrier so that the first workpiece surface 210 isadjacent to the front side carrier 300. Although FIG. 1A explicitlyshows a kerf area, it will be readily appreciated that according to afurther embodiment the kerf area 155 may be omitted and separation ofthe single chips may be accomplished using the separation trenches 140.

According to an embodiment, the separation trench 140 may be formed bydry etching, for example plasma etching. According to an embodiment, theseparation trench 140 may be formed before forming components of thesemiconductor devices. Optionally, the separation trench 140 may beformed by a high temperature process before forming those components ofthe semiconductor device which are sensitive to high temperature. Forexample, the separation trench 140 and the isolation trench 130 may beformed by a joint etching step. According to a further embodiment, theseparation trench 140 may be formed after thinning the semiconductorsubstrate 100.

Starting from the pre-processed workpiece shown in FIG. 1A, the backside 220 of the workpiece may be processed, by, optionally, forming ahard mask layer (stack) on the workpiece back side 220, followed by aphotoresist layer 240. Thereafter, openings 241 may be defined in thephotoresist layer 240. For example, the openings 241 may be defined soas to be aligned with the position of the filling made of the secondsacrificial layer 142 inside the separation trenches 140. Whenphotolithographically defining the openings 241, the isolation trenches130 may be used as a positioning mark. Thereafter, a further etchingstep may be performed so as to remove the first sacrificial layer 141.In the embodiment shown in FIG. 1B, since the isolation trench 130 has afunction different from that of the separation trench 140, no opening isformed so as to be aligned with the position of the second layer 132inside the isolation trench 130.

Thereafter, an etching step may be performed so as to define openings231 in the insulating layer 235. For example, wet etching withhydrofluoric acid (HF) may be performed so as to form the openings. FIG.1C shows an example of a resulting structure. The openings 231 mayapproximately have a width corresponding to a width of the separationtrenches 140. Nevertheless, the width of the openings 231 should belarge enough so that the whole cross-section of the second sacrificiallayer 142 is uncovered. Thereafter, the second sacrificial layer 142 isremoved from the separation trenches 140. For example, if polysilicon isused as the second sacrificial material, etching with KOH may beemployed. According to an embodiment, etching is performed from the backside 220 of the substrate. Hence, removing the at least one sacrificialmaterial from the trench comprises removing the at least one sacrificialmaterial from the bottom side 144 of the trench or from the back side220 of the substrate. Differently stated, removing the at least onesacrificial material may comprise etching the second sacrificial layer142 adjacent to the second main surface 120 of the substrate.

FIG. 1D shows an example of a resulting structure. As is shown, now agap 143 is formed between the sidewalls of the separation trench 140.The gap 143 extends from the second main surface 120 of thesemiconductor substrate 100 to approximately the first main surface 110of the semiconductor substrate 100. In the context of the presentapplication, the term “extends to approximately the first main surfaceof the semiconductor substrate” means that a small amount of materialmay remain within the gap, as long as the small amount does not inhibitor prevent a separation process which will be explained in thefollowing. For example, a remaining amount of material may have athickness (dimension in the vertical direction) of 0 to 500 nm.

Then, a further etching step, for example, an isotropic wet etching stepusing, for example, HF, may be performed so as to form openings 226 inthe insulating layer 225. FIG. 1E shows an example of a resultingstructure. The gap 143 now extends to the workpiece surface 210.

FIG. 1F shows an example of a resulting structure after removing theresidues of the photoresist layer 240. Then, the structure istransferred to a foil 400, which may be a foil suitable for separatingthe wafer into single chips. For example, the foil 400 may be made of asuitable plastic or polymer, as it is conventional.

FIG. 1G shows an example of a resulting structure. In the next step, thewafer may be separated into single chips by removing the foil 400according to generally known methods. By way of example, the foil 400may be stretched, and UV light may be irradiated from the back side 220to separate the single chips from the foil 400. Since the separation orisolation of the wafer into chips has been accomplished by the severaletching steps, it is not necessary to separate the single chips bydicing or sawing the substrate material 100 as well as the layers formedon the semiconductor substrate 100. As a consequence, the semiconductormaterial is less likely to be damaged due to the mechanical dicingprocess. Further, the width of the kerf area 155 may be reduced sincethere is less material necessary in order to perform the separationprocess. For example, the width of the kerf area 155 may beapproximately 30 to 40 μm.

According to a further embodiment, separation of the single chips may beaccomplished by removing the foil 400 according to known processes.

As has been explained above, according to an embodiment, the separationtrenches 140 may be defined at a very early processing stage of thesemiconductor device, before defining temperature sensitive components.As a result, the separation trenches can be etched using a hightemperature etching method. Further, the separation trenches 140 may bedefined photolithographically and may be etched by plasma etching, sothat, for example, crystal orientations do not need to be taken intoaccount during etching. As a result, it is possible to define thegeometry of the single chips photolithographically. Hence, any suitableshape of the single chips may be selected.

FIG. 1H shows an example of examples of shapes of the single chips. Forexample, as is shown in the left-hand part of FIG. 1 h, the chip area150 may be approximately rectangular, with rounded corners. Separationtrenches 140 are disposed between the chip area 150 and the kerf area155. The kerf area 155 is disposed between adjacent chip areas 150. Asshown in the right-hand portion of FIG. 1H, the chip area 150 may alsohave the shape of hexagon.

FIG. 11 illustrates a portion of a chip area 150 and a kerf area 155according to an embodiment. As is shown, the kerf area 155 may befurther patterned in a direction parallel to the plane of thecross-section illustrated in FIGS. 1A to 1H by forming additionalseparation grooves 156 extending in a direction perpendicularly withrespect to the separation trenches 140. For example, the separationgrooves 156 may be formed by etching the material in the kerf using anappropriate photoresist mask. According to an embodiment, the separationgrooves 156 may have a similar structure as the separation trenches 140that have been described hereinbefore. Due to the presence of theadditional separation grooves 156, the kerf area 155 may be patternedand isolated into small pieces so that during the next processing steps,large kerf areas are prevented from being separated from the wafer.

FIG. 1J shows a further embodiment, according to which, starting fromthe structure shown in FIG. 1G, a further etching step using, forexample, KOH is performed so as to define tapered openings 232. Due tothe etching with KOH, the tapered openings 232 are etched isotropically.

FIG. 2 illustrates a method according to a further embodiment. Astarting point for the further embodiment is a semiconductor substrate100 comprising a chip area 150 and a kerf area 155 as has been explainedabove with reference to FIG. 1A.

According to the embodiment shown in FIG. 2A, separation trenches 140are etched in the first main surface 110 of the semiconductor substrate100. Further, isolation trenches 130 may be defined in the first mainsurface 110 of the semiconductor substrate 100. An insulating material131, 141 may be disposed adjacent to the sidewalls of the isolationtrench 130 and the separation trench 140. Further, a second sacrificiallayer 142 such as polysilicon may be disposed in the interior of theseparation trenches 140. Differing from the embodiment shown in FIG. 1A,the semiconductor substrate 100 of FIG. 2A has not been thinned.Accordingly, the distance between the second main surface 120 and thefirst main surface 110 corresponds to the usual thickness of asemiconductor wafer. The isolation trenches 130 and the separationtrenches 140 do not extend to the second main surface 120. Theinsulating material 131, 141 is disposed in the isolation trench 130 andthe separation trench 140, respectively, to extend to a bottom side 144of these trenches. An insulating layer 225 is disposed over thesemiconductor device components disposed in the chip area 150. Theinsulating layer 225 may also be disposed over contacts and conductivelines 230, 221 disposed in the kerf area 155. According to theembodiment shown in FIG. 2A, no frontside carrier is attached to theworkpiece surface 210. Hence, test procedures and measurements may beperformed in the kerf area 155. The insulating layer 225 has a planarsurface. Thereafter, a photoresist layer 240 is formed over theinsulating layer 225 and is patterned to form an etching mask. Then, theoxide layer is etched to form openings 227.

FIG. 2B shows an example of a resulting structure. In a next step, aninsulating material such as a polyimide layer 228 is formed over theresulting structure after removing the residues of the photoresist layer240. Further, the polyimide layer 228 is photolithographicallypatterned. Due to the presence of the polyimide layer 228 which isdisposed over the patterned oxide layer, the wafer has increasedmechanical robustness.

FIG. 2C shows an example of a resulting structure. As is shown, in thechip area 150, the insulating layer 225 is covered by the polyimidelayer 228, whereas the insulating layer 225 disposed in the kerf area155 is uncovered. Further, at the position of the openings 227, thesemiconductor substrate material 100 and the separation trenches 140 areuncovered. A surface of the polyimide layer 228 forms a workpiecesurface 210. As is shown, the workpiece surface is not flat but has atopology. In the next step, a suitable carrier 300 such as a glasscarrier is attached to the main surface 210 of the workpiece 200.

Thereafter, the semiconductor substrate 100 is thinned from the secondmain surface 120. For example, the semiconductor substrate 100 may bethinned by mechanically grinding, followed by CMP so as to cure defectswhich may be caused due to the grinding. For example, about 750 μmthickness of the semiconductor wafer may be removed.

FIG. 2D shows an example of a resulting structure. The shownsemiconductor substrate 100 has a thickness of less than 100 μm. Forexample, the thickness may be about 10 to 100 μm. At a thickness largerthan 100 μm, it becomes difficult to define an isolation trench 130 andthe separation trench 140 having the desired geometry. Thereafter, aphotoresist layer 240 may be formed on the second surface 120 of thesemiconductor substrate 100 and may be patterned so as to form openings241.

FIG. 2E shows an example of a resulting structure. Then, optionally, anisotropic etching step, for example using KOH, may be performed so as toform openings 232 in the substrate material 100.

FIG. 2F shows an example of a resulting structure. Thereafter, anetching step is performed so as to remove the insulating layer (firstsacrificial layer) 141 from the separation trenches 140. According tothe embodiment of FIG. 2F, the first sacrificial layer 141 is removedfrom the bottom side 144 of the trench. Differently stated, etching isperformed from the back side 120 of the semiconductor substrate 100.Further, the residues of the photoresist layer 240 are removed.

FIG. 2G shows an example of a resulting structure. As is shown, a gap143 is formed between the sidewalls of the separation trench 140. Thegap 143 extends from the second main surface 120 to approximately thefirst main surface 110 of the semiconductor substrate 100. Residues ofthe sacrificial filling 142 are disposed within the gap 143. Thereafter,the semiconductor substrate 100 is transferred to a foil so that thesecond main surface 120 of the semiconductor substrate 100 is adjacentto the foil 400. The glass carrier 300 is removed from the surface ofthe workpiece 210 by conventional methods.

FIG. 2H shows an example of a resulting structure. Due to the transferprocess, the residues of the sacrificial material 142 may drop.Thereafter, the semiconductor substrate 100 may be separated into singlechips by removing the foil 400.

A starting point of a further embodiment is the structure illustrated inFIG. 3A which corresponds to the structure shown in FIG. 2D. Thecomponents shown in FIG. 3A correspond to those which have beenillustrated with reference to FIGS. 1 and 2. According to the embodimentillustrated in FIG. 3, the sidewall insulating material 141, which maybe for example, a silicon oxide layer, remains at the sidewalls of theseparation trenches 140 during the processing method so as establish asidewall oxide of the resulting chips. An insulating layer 235 such as asilicon oxide layer is formed on the second main surface 120 of thesemiconductor substrate 100. Optionally, metal pads may be formedadjacent to the second main surface 120 before forming the insulatinglayer 235 so as, for example, to be in contact with the conductivefilling 132 of the isolation trench 130. Thereafter, a photoresistmaterial 240 is formed over the insulating layer 235. Further, openings241 are defined in the photoresist material 240.

FIG. 3B shows an example of a resulting structure. Using the patternedphotoresist layer 240 as an etching mask, openings 231 are formed in theinsulating layer 235. The openings 241 in the photoresist layer 240 and,thus, the openings 231 in the insulating layer 235 are positions overthe sacrificial material 142 in the separation trenches 140.

FIG. 3C shows an example of a resulting structure. Thereafter, theresidues of the photoresist layer 240 are removed, followed by a wetetching step so as to remove the sacrificial material 142 from theseparation trenches 140. According to the embodiment of FIG. 3C, etchingis performed from the back side of the semiconductor substrate 100.

FIG. 3D shows an example of a resulting structure. As is shown, thesidewalls of the substrate material 100 and the second main surface 120are covered by the insulating layer 132 in the chip areas 150 and in thekerf area 155. Further, a gap 143 is disposed between the sidewalls ofthe separation trench 140. The gap 143 extends from the second mainsurface 120 to approximately the first main surface 110. Thereafter, theresulting structure is transferred to the foil 400. Further, the glasscarrier is removed from the surface 210 of the workpiece 200 accordingto a conventional method. According to embodiments, the kerf area 155may be patterned in more detail, e.g. in a plane disposed before orbehind the depicted plane of the drawing. According to this embodiment,it is possible that the patterned pieces of the kerf area 155 drops whenthe transfer to the foil 400 takes place.

Thereafter, the foil 400 may be removed so as to separate the processedsemiconductor substrate 100 into single chips.

Starting point for the embodiment which is illustrated in FIG. 4 is thestructure shown in FIG. 3A. According to this embodiment, an insulatinglayer disposed on the back side of the substrate is patterned. Afterremoving at least one sacrificial material from the trench, a conductivelayer is formed and patterned on the back side.

Starting from the structure shown in FIG. 3A, an insulating layer 235 isformed on the second main surface 120 of the semiconductor substrate100. Thereafter, a photoresist layer 240 is formed on the insulatinglayer 235 and patterned. FIG. 4A shows an example of a resultingstructure. Then, using the patterned photoresist layer 240 as an etchingmask, etching is performed so as to partially remove the insulatinglayer 235 and a further photoresist layer 245 is formed over theresulting surface. In a next step, openings 241 are defined in thephotoresist layer 240.

FIG. 4B shows an example of a resulting structure. As is shown, theinsulating layer 235 is formed over a portion of the second main surface120 of the semiconductor substrate 100. Thereafter, openings 231 areformed in the insulating layer 235, using the patterned photoresistlayer 240 as an etching mask.

FIG. 4C shows an example of a resulting structure. Then, the sacrificialmaterial 142 is removed from the separation trenches 140 by etching.According to the embodiment shown in FIG. 4C, etching is performed fromthe back side of the semiconductor substrate 100. FIG. 4D shows anexample of a resulting structure. As is shown, a gap 143 is disposedbetween the sidewalls of the separation trench 140. The gap 143 extendsfrom the second main surface 120 to approximately the first main surface110 of the semiconductor substrate 100. The residues of the photoresistmaterial 240, 245 are removed, and a metal layer 246 may be formedadjacent to the second main surface 120 of the semiconductor substrate100.

It is to be noted that the shown transistor 160 may be connected to themetal layer 246 by means of a connection which is disposed before orbehind the shown drawing plane. Thereafter, the semiconductor substrate100 is transferred to a foil 400 and the glass carrier 300 may beremoved. FIG. 4F shows an example of a resulting structure. Thereafter,the semiconductor wafer may be separated into single chips by removingthe foil 400.

FIG. 5 illustrates a method of manufacturing a semiconductor deviceaccording to an embodiment in a flowchart. As is shown, a method ofmanufacturing a semiconductor device comprises forming a separationtrench into a first main surface of a semiconductor substrate (S10),forming at least one sacrificial material in the separation trench(S20), removing substrate material from a second main surface of thesemiconductor substrate (S30), the second main surface being opposite tothe first main surface, so as to uncover a bottom side of the trench,and removing at least one sacrificial material from the trench (S40),comprising etching the at least one sacrificial material adjacent to thesecond main surface.

According to a different interpretation, a method of manufacturing asemiconductor device comprises forming a separation trench into a firstmain surface of a semiconductor substrate (S10), forming at least onesacrificial material in the separation trench (S20), removing substratematerial from a second main surface of the semiconductor substrate(S30), the second main surface being opposite to the first main surface,so as to uncover a bottom side of the trench, and removing at least onesacrificial material from the trench (S40) so as to form a gap betweensidewalls of the separation trench, the gap extending from the secondmain surface to approximately the first main surface.

FIGS. 6A and 6B illustrate a method of manufacturing a semiconductordevice according to a further embodiment. According to the embodiment,the semiconductor device is formed in a semiconductor substratecomprising a first main surface, and the semiconductor substrateincludes chip areas. As is shown in FIG. 6A, the method comprisesforming components of the semiconductor device in the first main surfacein the chip areas (S110), removing substrate material from a second mainsurface of the semiconductor substrate (S120), the second main surfacebeing opposite to the first main surface, forming a separation trenchinto a first main surface of a semiconductor substrate (S130) betweenadjacent chip areas, forming at least one sacrificial material in theseparation trench (S140), and, thereafter, removing at least onesacrificial material from the trench (S150). According to the embodimentshown in FIG. 6A, the substrate material is removed from the second mainsurface (S120) before forming the separation trench (S130), and theseparation trench is formed to extend to the second main surface.

According to the embodiment shown in FIG. 6B, the separation trench isformed (S130) and the at least one sacrificial material is formed (S140)before removing the substrate material (S120), and the substratematerial is removed so as to uncover a bottom side of the trench.

Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat a variety of alternate and/or equivalent implementations may besubstituted for the specific embodiments shown and described withoutdeparting from the scope of the present invention. This application isintended to cover any adaptations or variations of the specificembodiments discussed herein. Therefore, it is intended that thisinvention be limited only by the claims and the equivalents thereof.

What is claimed is:
 1. A method of manufacturing a semiconductor device,comprising: forming a separation trench into a first main surface of asemiconductor substrate; forming at least one sacrificial material inthe separation trench; removing substrate material from a second mainsurface of the semiconductor substrate, the second main surface beingopposite to the first main surface, so as to uncover a bottom side ofthe trench; and removing the at least one sacrificial material from thebottom side of the trench, after the substrate material has been removedfrom the second main surface.
 2. The method according to claim 1,wherein the separation trench is completely filled with the at least onesacrificial material.
 3. The method according to claim 1, furthercomprising forming an isolation trench in the semiconductor substrate,filling at least one insulating material in the isolation trench,wherein forming the separation trench and forming the isolation trenchcomprise joint processing methods.
 4. The method according to claim 1,wherein the sacrificial material comprises a first sacrificial layeradjacent to a sidewall of the separation trench, and a secondsacrificial layer, being different from the first sacrificial layer, thefirst sacrificial layer being made of an insulating material.
 5. Themethod according to claim 4, wherein removing at least one sacrificialmaterial comprises removing the second sacrificial layer.
 6. The methodaccording to claim 4, wherein removing at least one sacrificial materialcomprises removing the first sacrificial layer.
 7. The method accordingto claim 1, further comprising forming at least one transistor adjacentto the first main surface, wherein forming the separation trench isaccomplished before forming the transistor.
 8. The method according toclaim 1, further comprising forming at least one additional layer on thefirst main surface so as to define a workpiece surface, attaching thesemiconductor substrate to a front side carrier, so that the workpiecesurface is adjacent to the front side carrier, before removing the atleast one sacrificial material from the separation trench.
 9. The methodaccording to claim 8, further comprising: forming at least one layer onthe second main surface of the semiconductor substrate so as to define aworkpiece back side; and attaching the semiconductor substrate to a backside carrier, so that the workpiece back side is attached to the backside carrier, after removing the at least one sacrificial material fromthe separation trench.
 10. The method according to claim 9, whereinattaching the semiconductor substrate to the back side carrier isaccomplished after removing at least one sacrificial material from theseparation trench.
 11. The method according to claim 8, wherein theworkpiece surface has a planar surface when the front side carrier isattached to the semiconductor substrate.
 12. The method according toclaim 8, wherein the workpiece surface is a non-planar surface when thefront side carrier is attached to the semiconductor substrate.
 13. Themethod according to claim 5, further comprising forming and patterning afurther insulating layer on the second main surface before removing thesecond sacrificial layer, wherein the further insulating layer ispatterned in such a manner that the second main surface is completelycovered by the further insulating layer in portions between adjacentseparation trenches.
 14. The method of claim 1, further comprisingforming a contact trench extending from the first main surface to thesecond main surface, the contact trench being filled with at least oneconductive material, wherein forming the contact trench and forming theseparation trench comprise joint processing methods.
 15. The method ofclaim 1, further comprising: forming and patterning a further insulatinglayer on the second main surface after removing the substrate materialfrom the second main surface of the semiconductor substrate; and forminga conductive material on the second main surface after removing the atleast one sacrificial material from the trench.
 16. The method of claim1, wherein removing the at least one sacrificial material is performedso as to form a gap between sidewalls of the separation trench, the gapextending from the second main surface to approximately the first mainsurface.
 17. A semiconductor workpiece, comprising: a semiconductorsubstrate; at least two chip areas, components of semiconductor devicesbeing formed in the semiconductor substrate in the chip areas; and aseparation trench being disposed between adjacent chip areas, theseparation trench being formed in a first main surface of thesemiconductor substrate and extending from the first main surface to asecond main surface of the semiconductor substrate, the second mainsurface being disposed opposite to the first main surface, theseparation trench being filled with at least one sacrificial material.18. The semiconductor workpiece according to claim 17, furthercomprising a kerf area being disposed between adjacent chip areas. 19.The semiconductor workpiece according to claim 17, wherein thesacrificial material comprises a first sacrificial layer adjacent to asidewall of the separation trench, and a second sacrificial layer, beingdifferent from the first sacrificial layer, the first sacrificial layerbeing made of an insulating material.
 20. A method of manufacturing asemiconductor device in a semiconductor substrate comprising a firstmain surface, the semiconductor substrate including chip areas, themethod comprising: forming components of the semiconductor device in thefirst main surface in the chip areas; removing substrate material from asecond main surface of the semiconductor substrate, the second mainsurface being opposite to the first main surface; forming a separationtrench into a first main surface of a semiconductor substrate, theseparation trench being disposed between adjacent chip areas; forming atleast one sacrificial material in the separation trench; and removingthe at least one sacrificial material from the trench.
 21. The methodaccording to claim 20, wherein the substrate material is removed beforeforming the separation trench, and wherein the separation trench isformed to extend to the second main surface.
 22. The method according toclaim 20, wherein the separation trench is formed before removing thesubstrate material, and wherein the substrate material is removed so asto uncover a bottom side of the separation trench.